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. 2019 Feb 14;9(10):5592-5598.
doi: 10.1039/c8ra09627a. eCollection 2019 Feb 11.

Product distribution and mechanism of the OH- initiated tropospheric degradation of three CFC replacement candidates: CH3CF[double bond, length as m-dash]CH2, (CF3)2C[double bond, length as m-dash]CH2 and (E/ Z)-CF3CF[double bond, length as m-dash]CHF

Cynthia B Rivela  1 , Carmen M Tovar  2 , Rodrigo Gibilisco  2 , Mariano A Teruel  1 , Ian Barnes  2 , Peter Wiesen  2 , María B Blanco  1
Affiliations

Product distribution and mechanism of the OH- initiated tropospheric degradation of three CFC replacement candidates: CH3CF[double bond, length as m-dash]CH2, (CF3)2C[double bond, length as m-dash]CH2 and (E/ Z)-CF3CF[double bond, length as m-dash]CHF

Cynthia B Rivela et al. RSC Adv. .

Abstract

The OH radical initiated photodegradation of 2-fluoropropene (CH3CF[double bond, length as m-dash]CH2), 3,3,3-trifluoro-2-(tri-fluoromethyl)propene ((CF3)2C[double bond, length as m-dash]CH2) and (E/Z)-1,2,3,3,3-pentafluoropropene ((E/Z)-CF3CF[double bond, length as m-dash]CHF) has been investigated for the first time using a 1080 L quartz-glass environmental chamber at 298 ± 2 K and atmospheric pressure of synthetic air coupled with in situ FTIR spectroscopy to monitor reactants and products. The major products observed in the OH reaction were CH3C(O)F (98 ± 5)% together with HC(O)H (89 ± 7)% as a co-product, CF3C(O)F (103 ± 8)% together with HC(O)F (96 ± 7)% as a co-product and CF3C(O)CF3 (91 ± 8)% together with HC(O)H (98 ± 12)% as a co-product from the C1-C2 bond cleavage channel of the intermediate hydroxyalkoxy radical, formed by addition of OH to the terminal carbon of the double bond which is designated C1 of 2-fluoropropene, (E/Z)-1,2,3,3,3-pentafluoropropene and 3,3,3-trifluoro-2-(tri-fluoromethyl)propene, respectively. The present results are compared with previous studies for the reaction of OH with the separate isomers (E) and (Z) of 1,2,3,3,3-pentafluoropropene. In addition, atmospheric implications of the reactions studied are discussed.

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Conflict of interest statement

There are no conflicts to declare.

Figures

Fig. 1
Fig. 1. Mechanism for the reaction of 2-fluoropropene with OH radicals via addition of OH to the double bond.
Fig. 2
Fig. 2. Mechanism for the reaction of 3,3,3-trifluoro-2-(trifluoromethyl)propene with OH radicals via addition of OH to the double bond.
Fig. 3
Fig. 3. Mechanism for the reaction of 1,2,3,3,3-pentafluoropropene (mixture E/Z) with OH radicals via addition of OH to the double bond.
Fig. 4
Fig. 4. Panel A shows the infrared product spectrum obtained from a 2-fluoropropene/H2O2/air reaction mixture after UV irradiation after subtraction of 2-fluoropropene bands. Panels B and C show reference spectra of acetyl fluoride and formaldehyde, respectively. Panel D shows the residual product spectrum obtained after subtraction of features due to the reference spectra from the spectrum in panel A.
Fig. 5
Fig. 5. Plots of the concentrations of the reaction products formyl fluoride and trifluoroacetylfluoride as a function of reacted 1,2,3,3,3-pentafluoropropene (mixture cis/trans) obtained from UV photolysis of 1,2,3,3,3-pentafluoropropene (mixture E/Z)/H2O2/air reaction mixtures.
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